MySQL is graying in several metaphorical ways. Of course, it is simply
getting older--aren't we all? But it is by no means over the hill.
More significantly, its adherents are getting less colorful and
reflect instead the grayness of the corporate settings it is
conquering. Finally, MySQL is graying the distinctions that separated
it from Oracle and other heavy-duty database engines. MySQL, in short,
is becoming conventional.

The early achievements of this disruptive technology were to bring a
high-performance relational database down from the top shelf where
only those of means could afford it, and put it in the hands of
students, enterpreneurs working out of their homes, and modest web
site developers. This was a revolution dubbed situated software by Clay Shirky. Although MySQL was already being used by sites that
could afford more expensive databases (and the computer systems and
expert administrators who came in tow), these did not drive its
initial popularity.

Now MySQL AB has built a formidable marketing machine and carried
their product into the database mainstream, following a path similar
to Linux. Their trappings are starting to evince familiar themes. They
have salespeople in at least a dozen cities around North
America. Their new support and update mechanism, MySQL Network,
reminds me of a similarly named support system from Red Hat. MySQL's
development of an online FAQ called a Knowledge Base, and the slogan
"MySQL Everywhere" plastered all around this conference, are
reminiscent of another large software vendor.

But MySQL AB has not forgotten the little guys who want a DBMS that
runs lean and fast, with near-zero administration. These users will
probably continue to be its largest base. Significantly, under the
conventional trappings I mentioned, I believe MySQL AB is still
structured in a fundamentally different way from a conventional
propriety vendor, and is still behaving like a network of brilliant
independent software developers. They have always listened closely to
their users--you can see that at their conferences, where dozens of
developers turn up in distinctive shirts and attract flocks of
petitioners for new features--but they now are listening to paying
customers in the same intense, investigative manner.

For instance, I saw one of their leading engineers walk around an
evening reception recruiting representatives from international
customers to sit in on a session about internationalization, just so
he could hear their perspective on some problems he had been told by
other customers.

It takes a certain financial and time commitment to attend a
conference, so for those who pony up the money to do so, the theme at
this one is "bigger and better." Sessions on Java interfaces,
clustering, scaling, high availability, and replication decorate the
calendar for the next few days. One panel is even called "Challenges
in the Enterprise."

And what are the newest features MySQL is pushing hardest? There are
no breakthroughs here (and I wouldn't expect any, because relational
databases are a mature area in a research sense). The announcements
focus on things that competitors have had for years: stored
procedures, triggers, views. MySQL is not leading the conquest of new
territories. Rather, MySQL is catching up. That's something they're
proud of, and rightfully so.

I attended one session last night on a feature that will implement a
tiny snippet of the SQL standard, XPath support. In effect, MySQL,
which has always understood the SQL language, is learning a second
language--not a natural language (although MySQL offers increasing
support for character sets and other internationalization features)
but the complex world of XPath.

I find this feature an odd way to support XML. Most XML users carry
out XML/database interaction by using Java or some other programming
tool to break down the XML into constituent pieces of test and store
those pieces in a database structure that mirrors the XML. But SQL's
XPath support buries the XML without alteration into a field in the
database.

The idea of XPath support in the database is that you start by storing
a string such as
<p>Why do <em>you</em> want to represent <em>structured text</em>?</p>
bodily in a text column. This text column can be any standard text
datatype in SQL (although MySQL will add a special XML tag eventually,
to support validation and some optimizations).

In itself, this doesn't help deal with XML. But MySQL will also
provide a couple functions such as ExtractValue and UpdateXML that
manipulate the XML with XPath queries. You could tell it to extract or
change, for example, the second <em> entity in the string just
shown. Full text searches can reduce the time it takes to search large
collections of XML by two orders of magnitude, in comparison to
database queries without indexes.

The design of the XPath support is oddly disconnected from the
traditional structures of a relational database. As already shown, the
storage model jams all the XML into a single column, so that the XML
structure is handled independently from the schema of the table.
Furthermore, an XPath query that returns multiple strings from
different parts of the XML document concatenates them together,
space-separated, in a single row. I would have expected them to be
granted individual rows in the results.

There are many uses for XPath support in a database. One could extract
and display all the titles of different documents. One could run a
traditional SELECT to retrieve data from other columns or tables and
join it to XML content. One could find everything within
<price> tags and let the database perform some
calculations such as averaging. The more XML processing you can do in
the database, the less data has to be sent over the wire to the
client.

This new MySQL feature--not planned until 5.1 or even later--is
probably less useful with data-crunching XML (which has many small
pieces of text within multiple tags) than with documents, which are
flatter and have a high ratio of content to tagging. However, one
participant in last night's BOF suggested the feature could be applied
to storing SOAP queries too.

MySQL's turn to the mainstream is being reciprocated by its intended
audience. Attendance at yesterday's tutorials was impressive; a couple
tutorials sold out, and the halls were filled with people at break
time. Today's sessions and exhibitors will draw even more.

Andy Oram
is an editor for O'Reilly Media, specializing in Linux and
free software books, and a member of Computer Professionals for Social
Responsibility. His web site is www.praxagora.com/andyo.

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